| Round 4 on 2018/09/15 at 21h |
| Bo. | 8 | Alta Floresta do Oeste | Rtg | - | 6 | Cerejeiras | Rtg | 1½:2½ |
|---|
| 1.1 | | | Breno Maximiliano Gregolin |
| 0 | - | | | 0 | 0 - 1 |
| 1.2 | | | 0 | - | | | Alcimary Mayago Oliveira Portela |
| 0 | 0 - 1 |
| 1.3 | | | Jederson Nogueira de Paula |
| 0 | - | | | 0 | 1 - 0 |
| 1.4 | | | 0 | - | | | Gabriel Candido de Oliveira |
| 0 | ½ - ½ |
| Bo. | 7 | Cacoal | Rtg | - | 5 | Nova Mamore | Rtg | 3 : 1 |
|---|
| 2.1 | | | 0 | - | | | Walterio Carlos Araujo Rocha |
| 0 | ½ - ½ |
| 2.2 | | | 0 | - | | | Rubens Batista de Freitas |
| 0 | 1 - 0 |
| 2.3 | | | 0 | - | | | Anjossendre Honzelnan Silva |
| 0 | ½ - ½ |
| 2.4 | | | Carlos Alejandro Martinez |
| 0 | - | | | 0 | 1 - 0 |
| Bo. | 1 | Porto Velho | Rtg | - | 4 | Vilhena | Rtg | 2 : 2 |
|---|
| 3.1 | | | Victor Gabriel Candido de Oliveira |
| 0 | - | | | 0 | 1 - 0 |
| 3.2 | | | 0 | - | | | 0 | 0 - 1 |
| 3.3 | | | Melquizedeque de Melo Alemão |
| 0 | - | | | 0 | 0 - 1 |
| 3.4 | | | Vinicius Rian Rodrigues da Silva |
| 0 | - | | | Francisco Fagundes da Silva |
| 0 | 1 - 0 |
| Bo. | 2 | Pimenta Bueno | Rtg | - | 3 | Ji Paraná | Rtg | 2 : 2 |
|---|
| 4.1 | | | 0 | - | | | 0 | 1 - 0 |
| 4.2 | | | 0 | - | | | 0 | 0 - 1 |
| 4.3 | | | Miguel Casa Grande dos Santos |
| 0 | - | | | Lucas Diego de Oliveira Santos |
| 0 | 1 - 0 |
| 4.4 | | | 0 | - | | | 0 | - - + |